34 



PROTOZOA 



Diagrammatic optical section of a Ciliate Protozoon, showing all structures 

 except the contractile vacuoles. a, nucleus; b, paranucleus (so-called 

 nucleolus) ; c, cortical substance ; D, extremely delicate cuticle ; E, 

 medullary (more fluid) protoplasm ; /, cilia; y, trichocysts ; ft, filaments 

 ejected from the trichocysts ; ', oral aperture ; k, drop of water contain- 

 ing food-particles, about to sink into the medullary substance and form 

 a food-vacuole ; I, m, n, o, food-vacuoles, the successive order of their 

 formation corresponding to the alphabetical sequence of the letters ; the 

 arrows indicate the direction of the movement of rotation of the medul- 

 lary protoplasm ; p, pharynx. 3. Outline of a Ciliate (Paramcecium), to 

 show the form and position of the contractile vacuoles. 4-7. 



Successive stages in the periodic formation of the contractile vacuoles. 

 The ray-like vacuoles discharge their contents into the central vacuole, 

 which then itself bursts to the exterior. 8-15. Diagrams of the changes 

 undergone by the nucleus and paranucleus of a typical Ciliate during 

 and immediately after conjugation : N, nucleus; pn, paranucleus; 8, 

 condition before conjugation ; 9, conjugation effected ; both nucleus 

 and paranucleus in each animal elongate and become fibrillated ; 10, 

 two spherical paranuclei pn* in each, two dividing or divided nuclei 

 N* ; 11, the spherical paranuclei have become fusiform ; 12, there 

 are now four paranuclei in each (pn* and pn 1 '), and & nucleus 

 broken into four or even more fragments ; 13, the two paranuclei 

 marked pn* in 12 have united in each animal to form the new nucleus 

 pn' ; the nuclear fragments are still numerous ; 14, after cessation 

 of conjugation the nuclear fragments N and the two unfused paranuclear 

 pieces pn* are still present ; 15, from a part or all of the fragments 

 the new paranucleus is in process of formation, the new nucleus (pn 1 = N) 

 is large and elongated. 10. Diagram of a Ciliate in process of trans- 



verse fission. 17. Condition of the nucleus N, and of the paranucleus 



pn in Paramcecium aurelia after cessation of conjugation as observed 

 by Butschli. 18. Stylonichia mytilus (one of the Hypotricha), 



showing endoparasitic unicellular organisms 6, formerly mistaken for 

 spores ; a, nuclei (after conjugation and breaking up). 



Fam. 7. 



Genera. Astylozoon, Engelm. ; Ophnjoscolex, Stein. 



Sub-order 2. SEDENTARIA, animals always attached or sedentary 

 during the chief part of the life-history. 



Fam. 1. VORTICELLID^;. Animals ovate, campanulate, or sub- 

 cylindrical ; oral aperture terminal, eccentric, associated with a 

 spiral fringe of adoral cilia, the right limb of which descends into 

 the oral aperture, the left limb encircling a more or less elevated 

 protrusible and retractile ciliary disk. 



Sub-family 1. Vorticelliuse : animalcules naked. 



a. Solitary forms. 



Genera. Gcrda, Cl. andL. ; Scyphidia, Dujnrd. ; Spirochona, Stein 

 (sessile with peristome in the form of a spirally convolute mem- 

 branous expansion, Fig. XXIII. 10) ; Pyxidium, Kent (with a 

 non-retractile stalk) ; Vorticella, Linn, (with a hollow stalk in 

 which is a contractile muscular filament). 



j8. Forming dendriform colonies. 



Genera. Carchesium, Ehr. (Fig. XXIII. 18, with contractile 

 stalks) ; Zoothammium, Ehr. (contractile stalks) ; Epistylis, Ehr. 

 (stalk rigid) ; Opercularia, Stein (stalk rigid, ciliated disk oblique ; 

 an elongated peristomial collar, Fig. XXIII. 20). 



Sub-family 2. Vaginicolinae : animalcules secreting firm cup-like 

 or tube-like membranous shells. 



Genera. Vaginicola, Lamarck (no internal valve); Thuricola, 

 Kent (with a door-like valve to the tube, Fig. XXIII. 25, 26) ; 

 Cothurina, Ehr. (lorica or shell pediculate ; no operculum); Pyxicola, 

 Kent (lorica pedunculate, animal carrying dorsally a horny oper- 

 culum, Fig. XXIII. 21, 22). 



Sub-family 3. Ophrydina : animalcules secreting a soft gelatinous 

 envelope. 



Genera. Ophionella, Kent; Ophrydium, Ehr. 



ORDER 2. HETEROTRICHA, Stein. 



Characters. A band or spiral or circlet of long cilia is 

 developed in relation to the mouth (the heterotrichous band) 

 corresponding to the adoral circlet of Peritricha; the rest of the 

 body is uniformly beset with short cilia. 



a. Heterotrichal band circular. 



Genera (selected). Tinlinnus, Schranck (Fig. XXIII. 3); Tri- 

 chodinopsis, Cl. and L. ; Codonella, Haeck. (with a peri-oral fringe 

 of lappet-like processes) ; Calccolus, Diesing. 



j8. Heterotrichal band spiral. 



Genera (selected). Stenlor, Oken (Fig. XXIII. 2) ; Blepharisma, 

 Perty (with an undulating membrane along the oral groove); 

 Spirostomum, Ehr. (oral groove linear and elongate, Fig. XXIII. 

 1); Leucophrys, Ehr. (oral groove very short). 



y. Heterotrichal band in the form of a simple straight or oblique 

 adoral fringe of long cilia. 



Genera (selected).- Sursaria, Miiller ; Nyctothcrus, Leidy (with 

 well-developed alimentary tract and anus, Fig. XXIV. 22) ; Balan- 

 tidium, Cl. and L. (B. colt parasitic in the human intestine). 



ORDER 3. HOLOTKICHA, Stein. 



Characters. There is no special adoral fringe of larger cilia, nor 

 a band-like arrangement of cilia upon any part of the body ; short 

 cilia of nearly equal size are uniformly disposed all over the surface. 

 The adoral cilia sometimes a little longer than the rest. 



a. With no membraniform expansion of the body wall. 



Genera. Paranuecium, Ehr. (Fig. XXV. 1, 2) ; Prorodon, Ehr. 



(Fig. XXIV. 13); Coleps, Ehr. ; Enchelys, Ehr.; Trachelocerca, Ehr.; 

 Trachelius, Ehr. ; Amphileptus, Ehr. ; Icthyophthirius, Fouquet 

 (Fig. XXIV. 15). 



j8. Body with a projecting membrane, often vibratile. 



Genera. Ophryoglena, Ehr.; Colpidium, Stein; Lembus, Cohn ; 

 Trichonympha, Leidy (an exceptionally modified form, parasitic, 

 Fig. XXIV. 3). 



y. Isolated parasitic forms, devoid of a mouth. 



Genera. Opalina, Purkinje (nuclei numerous, no contractile 

 vaeuole, Fig. XXIV. 4 to 8) ; Bcnedenia, Foett. ; Opalinopsis, 

 Foett. (Fig. XXIV. 1, 2); Anoplophrya, Stein (large axial nucleus, 

 numerous contractile vaeuoles in two linear series, Fig. XXIV. 9 

 10) ; Haptophrya, Stein ; Hvplitvphrya, Stein. 



ORDER 4. HYPOTRICHA, Stein. 



Characters. Ciliata in which the body is flattened and the 

 locomotive cilia are confined to the ventral surface, and are often 

 modified and enlarged to the condition of muscular appendages 

 (setae so-called). Usually an adoral band of cilia, like that of 

 Heterotricha. Dorsal surface smooth or provided with tactile 

 hairs only. Mouth and anus conspicuously developed. 



a. Cilia of the ventral surface uniform, fine, and vibratile. 



Genera. Chilodon, Ehr. ; Loxodes, Ehr. ; Dysleria, Huxl. ; 

 Huxley a, Cl. and L. 



/3. Cilia of the ventral surface variously modified as seta? 

 (muscular appendages), styles, or uncini. 



Genera. Stylonichia, Ehr. (Fig. XXV. 18); Oxytricha, Ehr.; 

 Euplotes, Ehr. (Fig. XXIV. 20, 21). 



Further remarks on the Ciliata. The Ciliata have recently 

 formed the subject of an exhaustive treatise by Mr Saville Kent (71) 

 which is accessible to English readers. On the other hand Prof. 

 Butschli has not yet dealt with them in his admirable critical 

 treatise on the Protozoa. Hence a large space has not been devoted 

 in this article to the systematic classification and enumeration of 

 their genera. See (79) and (93). 



One of the most interesting features presented by the group is 

 the presence in many of a cell anus as well as a cell mouth (Fig. 

 XXIV. 22, d). In those devoid of an anus the undigested 

 remnants of food are expelled either by a temporary aperture on 

 the body-surface or by one opening into the base of the pharynx. 

 In many parasitic Ciliata, as in higher animal parasites, such as 

 the Cestoid worms, a mouth is dispensed with, nutriment being 

 taken by general imbibition and not in the solid form. Many 

 Ciliata develop chlorophyll corpuscles of definite biconcave shape, 

 and presumably have so far a capacity for vegetal nutrition. In 

 Vorticella vlridis the chlorophyll is uniformly diffused in the pro- 

 toplasm and is not in the form of corpuscles (72). 



The formation of tubes or shells and in connexion therewith of 

 colonies is common among the Peritricha and Heterotricha. The 

 cuticle may give rise to structures of some solidity in the form of 

 hooks or tooth-like processes, or as a lining to the pharynx (Fig. 

 XXIV. 12). 



The phenomena connected with conjugation and reproduction 

 are very remarkable, and have given rise to numerous misconcep- 

 tions. They are not yet sufficiently understood. It cannot be 

 surely asserted that any Ciliate is at the present time known to 

 break up, after encystment or otherwise, into a number of spores, 

 although this was at one time supposed to be the rule. Icthyoph- 

 thirius (Fig. XXIV. 15 to 18) and some Vorticella; (76) have been 

 stated, even recently, to present this phenomenon ; but it is not 

 impossible that the observations are defective. The only approach 

 to a rapid breaking up into spores is the multiple formation (eight) 

 of microgonidia or microzooids in Vorticellida; (Fig. XXIII. 11, 

 12); otherwise the result of the most recent observations appears to 

 be that the Ciliata multiply only by binary fission, which is very 

 frequent among them (longitudinal in the Peritricha, transverse 

 to the long axis in the others). 



Several cases of supposed formation of spores within an adult 

 Ciliate and of the production endogenously of numerous "acineti- 

 form young " have been shown to be cases of parasitism, minute 

 unicellular parasites, e.g., parasitic Acineta; (such as Sphterophrya 

 described and figured in Fig. XXVI. ) being mistaken for the young. 



The phenomenon of conjugation is frequent in the Ciliata, and is 

 either temporary, followed by a separation of the fused individuals, 

 as in most cases, or permanent, as in the case of the fertilization 

 of normal individuals by the microgonidia of Vorticellidae. 



Since the process of conjugation or copulation is not followed 

 by a formation of spores, it is supposed to have merely a fertilizing 

 effect on the temporarily conjoined individuals, which nourish 

 themselves and multiply by binary fission more actively after the 

 process than before (hence termed "rejuvenescence)." 



Remarkable changes have been from time to time observed in 

 the nuclei of Ciliata during or subsequently to conjugation, and 

 these were erroneously interpreted by Balbiani (73) as indicating 

 the formation of spermatozoa and ova. The nuclei exhibit at one 

 period great elongation and a distinct fibrillation, as in the dividing 



